1. Field of the Invention
The present invention relates generally to the winding of filamentary materials onto a spool, and, more particularly, to a method and apparatus for the winding of filamentary materials into a tandem stack of flat coils from a single filament.
2. Description of Related Ar
There are many situations in which it is necessary to unwind from a prefabricated spool, an extended length of either a metal wire or an optical fiber at a rapid rate and in such a manner as not to crimp, distort or over-stress the filamentary material. For example, certain present-day missiles include a stored spool of a filament which, upon launching of the missile, is paid out and remains interconnected with apparatus at the launch site. The target scene information and missile guidance commands are transmitted via the filament data link for the entire or portion of the missile travel. Conventional cylindrical layered windings such as typically encountered in the winding of transformers or in the textile industry, for example, are not fully satisfactory for use with filaments such as optical fibers and may be accompanied by several difficulties in use. For example, on rapid payout of an optical fiber from a conventional spool which is cylindrically wound, there is a high lateral friction drag on the filament which produces heat with possible damage to the fiber from that source resulting in data link failure or undesirable signal modulation. Also, as the result of shelf storage or temperature cycling during storage, the winding pattern may collapse or slump which can prevent smooth payout on dispense posing a risk of damage. Still further, there is an inherent requirement in cylindrical layered winding of fiber crossover areas between the layers, and this produces what is referred to as "microbending" resulting in significant optical signal loss.
In an attempt to overcome the deficiencies of cylindrical layered windings, spools have been made up by winding a tandem stack of flat coils, each coil consisting of a fixed length of fiber wound into a spiral. Although this approach overcomes the noted difficulties with cylindrical layered winding, until now a practical and high-speed process of making flat coil windings from a single continuous fiber has not been achieved with previous known techniques all found to be excessively labor intensive and tedious.